JP6545657B2 - Separation method of anions - Google Patents

Description

  The present invention relates to an anion separation method for separating, concentrating and recovering useful anions other than fluorine from a raw material liquid containing fluorine by electrodialysis in a product liquid.

  For example, rare resources such as iodine may be contained in industrial effluents at a concentration of at least 10,000 times higher than that existing as natural resources in brackish water after recovery of water-soluble natural gas. Recovering resources is very effective from both economic and environmental points of view.

  However, industrial waste liquid may contain fluorine in some cases, in which case separation and removal of fluorine impairs the economic efficiency, making it difficult to recover scarce resources.

  In addition, in many chemical products derived from salt water and other seawater, the incorporation of fluorine is slight but unavoidable.

  Here, it is known that sodium chloride produced by electrodialysis from seawater has a lower fluorine content than sodium chloride (sunlight salt) produced without using the electrodialysis method.

  From this, in the electrodialysis method, although it is possible to remove part of the fluorine while separating and concentrating the chloride ion, it is considered that the fluorine can not be completely removed from the chloride ion concentrate.

  In the electrodialysis method, the raw material liquid is made acidic to reduce the ionization degree of hydrogen fluoride, whereby the electric transfer of fluoride ion from the raw material chamber (raw material liquid side) to the product room (concentrated liquid side) is performed. It is also known that it can be reduced.

  However, because hydrogen fluoride molecules are small in size, they pass non-electrically through cation exchange membranes and anion exchange membranes, even if they are not ionized, as they move due to diffusion or water movement caused by an osmotic pressure difference. Then move from the ingredient room to the product room. Therefore, fluorine can not be completely removed from the concentrated solution by the conventional electrodialysis method.

  Although several steps of electrodialysis can reduce the concentration of fluorine in the concentrate depending on the number of stages, it is not industrially reasonable.

  As a method for selectively removing fluoride ions from the solution, as shown in Patent Documents 1 and 2, a coprecipitation method using calcium hydroxide, aluminum sulfate or the like is known.

  Further, as shown in Non-Patent Documents 1 and 2 and Patent Document 3, there is known a method of using a fluorine removing agent such as ettringite which can selectively adsorb fluorine.

  Furthermore, as shown in Patent Document 4, in the electrodialysis method, mineral acid is added to the raw material liquid to make it acidic as a method of separating boric acid which is not fluorine but is a useful anion but not fluoride. It is known that the transfer of boric acid can be limited.

JP 2005-296888 A Patent No. 4956905 gazette JP, 2015-97995, A JP, 2009-23847, A

Immobilization Mechanism of Fluorine in Aqueous Solution with Calcium Aluminates, ISIJ International, 2001, Vol. 41, no. 5, p. 506-512 Toshimitsu Tokumitsu, "Development of Ceramics for Environmental Purification", September 2006, Graduate School of Natural Science and Technology, Niigata University

  Although any method of patent documents 1 to 3 and non-patent documents 1 and 2 is an excellent method for removing fluorine, the raw material liquid adheres to the slurry of the fluorine adsorbent and a loss of several% to several tens% is caused. It is not a rational method for the purpose of resource recovery because it will occur.

  In addition, since the introduction of the fluorine removing agent, curing and filtration, etc. must be performed by so-called internal preparation, the process becomes long.

  Furthermore, coprecipitation method requires skilled techniques for pH control and the like, which increases the work load.

  Further, in the method of Patent Document 2, in the case of fluoride ion, as described above, separation is insufficient only by pH adjustment.

  Therefore, when useful anions are separated from the fluorine-containing raw material solution by electrodialysis, movement of the fluorine to the product chamber (concentrate) side is suppressed to separate only anions, and useful except for fluorine. There has been a need for a method of efficiently obtaining an anion concentrate.

  The present invention has been made in view of these points, and it is an object of the present invention to provide a method of separating anions from which an anion concentrate can be obtained efficiently.

The method for separating anions according to claim 1 is a method for separating anions , comprising separating and concentrating anions into a product liquid from a raw material liquid containing fluorine together with anions other than fluorine by electrodialysis. As a dialysis method, a first anion exchange membrane, a first cation exchange membrane, a second anion exchange membrane, and a second cation exchange membrane are sequentially disposed, and these ion exchange membranes sequentially form a secondary salt. An electrodialysis method using an electrodialysis tank divided into a chamber, an auxiliary material chamber, a product chamber and a raw material chamber, and in which four chambers from the auxiliary salt chamber to the second cation exchange membrane are repeatedly arranged as one set, Using a three-chamber electrodialysis method without a salt chamber or an electrodialysis method without a secondary material chamber using a bipolar membrane , add a cation that forms a complex with fluorine to the raw material solution, and add a raw material solution No precipitation of precipitated cations It is intended to maintain.

According to a second aspect of the present invention, in the anion separation method of the first aspect, the cation which forms a complex with fluorine is a polyvalent cation .

The method for separating an anion according to claim 3 is the method for separating an anion according to claim 1 or 2, wherein the cation forming a complex with fluorine is aluminum ion, polyaluminum ion, zirconium oxide ion, zirconium. It is at least one of ion, calcium ion, magnesium ion, iron ion, scandium ion, gallium ion, gadolinium ion, indium ion, vanadium ion and lanthanum ion .

  The method for separating anions according to claim 4 is the method for separating anions according to any one of claims 1 to 3, wherein the fluorine concentration of the raw material liquid is 1000 mg / L or less, and the fluorine concentration in the product liquid is Is 2 mg / L or less.

  The method for separating anions according to claim 5 is the method for separating anions according to any one of claims 1 to 4, wherein the amount of increase in fluorine concentration in the product liquid before and after electrodialysis is 1 mg / L. It is the following.

  The method for separating anions according to claim 6 is the method for separating anions according to any one of claims 1 to 5, wherein the concentration of anions other than fluorine in the raw material liquid is 1% or more.

  The method for separating an anion according to claim 7 is the method for separating an anion according to any one of claims 1 to 6, wherein the anion is an iodide ion, a bromide ion, a chloride ion and an organic acid ion. It is at least one of them.

  The method for separating an anion according to claim 8 is the method for separating an anion according to any one of claims 1 to 7, wherein the cation is 0 per metal in total with respect to the fluorine contained in the raw material liquid. .3 or more moles are added.

According to the present invention, as the electrodialysis method, a first anion exchange membrane, a first cation exchange membrane, a second anion exchange membrane and a second cation exchange membrane are sequentially disposed, and these ion exchange Electrodialysis tank divided into a sub-salt chamber, a sub-material chamber, a product chamber, a raw material chamber in order by a membrane, and four chambers from the sub-salt chamber to the second cation exchange membrane are repeatedly arranged as one set The cation is added to the raw material solution by using an electrodialysis method using an electrolyte, a three-chamber electrodialysis method without an auxiliary salt chamber, or an electrodialysis method without an auxiliary material chamber using a bipolar membrane , and the cation and fluorine And form a cation type complex, and restrict the movement of the fluorine contained in the raw material solution to the concentrate side through the anion exchange membrane, so that anions other than fluorine contained in the raw material solution can be anionized. Because it can be efficiently separated into the concentrate through the exchange membrane, Rate to obtain an anion concentrate.

It is an explanatory view showing the composition of the electrodialysis tank for enforcing the separation method of the anion concerning the 1 embodiment of the present invention.

  Hereinafter, the configuration of an embodiment of the present invention will be described in detail with reference to the drawings.

  In the method for separating anions according to one embodiment of the present invention, useful anions are concentrated in a concentrate (product liquid) by electrodialysis from a raw material solution such as industrial waste liquid containing fluorine together with useful anions. To separate and concentrate.

  The electrodialysis tank 1 grade | etc., As an electrodialysis apparatus shown in FIG. 1 is used for an electrodialysis method.

  In the electrodialysis tank 1, a pair of electrodes 2 and 3 are disposed on both sides, and the electrode 2 which is one of the electrodes 2 and 3 is an anode (positive electrode), and the other electrode 3 is a cathode (negative electrode) Be done.

  Moreover, the electrodialysis tank 1 is provided with the chamber frame 4 as a rectangular frame body by planar view which has a notch part which is not shown in figure.

  Electrodes 2 and 3 are attached to the inside of both ends along the longitudinal direction of the chamber frame 4, and a cathode exchange chamber 5 is disposed on the cathode side of the electrode 2 of the electrodialysis tank 1. An electrode chamber 8 on the negative electrode side is constituted by the cation exchange membrane 7 disposed on the anode side of the electrode 3.

  Between the electrode chambers 6 and 8, the first anion exchange membrane 11, the first cation exchange membrane 12, the second anion exchange membrane 13, and the electrode 3 from the electrode 2 side to the electrode 3 side, A second cation exchange membrane 14 is arranged sequentially. The ion exchange membrane is partitioned from the electrode chamber 6 toward the electrode chamber 8 into the auxiliary salt chamber 15, the auxiliary material chamber 16, the product chamber 17 and the raw material chamber 18. Then, four to four membranes from the auxiliary salt compartment 15 to the second cation exchange membrane 14 form one set, and several to several hundreds of sets (n sets) are repeatedly arranged.

  Further, the first cation exchange membrane 21 is disposed on the cathode side of the raw material chamber 18 and is partitioned as a sub salt chamber 22.

  Furthermore, a cation exchange membrane 7 is disposed on the cathode side of the sub salt chamber 22 and is partitioned as a sub salt chamber 23, and the sub salt chamber 23 is adjacent to the electrode chamber 8.

  Each of the ion exchange membranes is tightened on both sides of the chamber frame 4 in a tensioned state by being pulled along each of the longitudinal direction and the vertical direction which is the width direction of the chamber frame 4 in order to give tension. It is fixed.

  Further, a liquid supply port and a liquid discharge port (not shown) communicating with the inside of the chamber frame 4 are provided on the inner surface of the chamber frame 4 in each liquid chamber partitioned by each ion exchange membrane. Further, in the chamber frame 4, a spacer (not shown) having a distribution function to make the thickness in the chamber frame 4 uniform is provided.

  As the first anion exchange membrane 11 and the second anion exchange membrane 13, for example, a general strong basic styrene-divinylbenzene based uniform anion exchange membrane or the like is used. Specifically, as the first anion exchange membrane 11 and the second anion exchange membrane 13, for example, a selamion AMV membrane (manufactured by Asahi Glass Co., Ltd.), Neosepta AM-2 membrane (manufactured by Tokuyama Co., Ltd.), Aciplex A101 A membrane (manufactured by Asahi Kasei Corporation) or the like is used.

In addition, by using a monovalent anion selective permeable membrane which is a membrane having enhanced selectivity of monovalent anions as the second anion exchange membrane 13, monovalent anions such as iodide ion (I ⁻ ) can be obtained. Depending on the application, it is more effective because its selective permeability is higher. As the monovalent anion selectively permeable membrane, for example, a Seremion ASV membrane (manufactured by Asahi Glass Co., Ltd.), Neosepta ACS membrane (manufactured by Tokuyama Co., Ltd.), Aciplex A192 membrane (manufactured by Asahi Kasei Corp.), etc. are used.

And, as the first anion exchange membrane 11, a general anion selective permeable membrane which transmits arbitrary anions other than monovalent anions and a monovalent anion which selectively permeates monovalent anions There is an anion selective permeable membrane. When polyvalent anions such as sulfate ion (SO ₄ ^2- ) are used as anions in the auxiliary material solution, a general anion selective permeation membrane can be used. Moreover, when using monovalent anions, such as a chloride ion (Cl < ^- >), a monovalent anion selectively permeable membrane can also be used.

  As the cation exchange membranes 5, 7, 21 and the first cation exchange membrane 12 and the second cation exchange membrane 14, for example, a strongly acidic styrene-divinylbenzene homogeneous cation exchange membrane or the like is used. Specifically, these cation exchange membranes 5, 7, 21 and the first cation exchange membrane 12 and the second cation exchange membrane 14 may be, for example, a selamion CMV membrane (manufactured by Asahi Glass Co., Ltd.), Neosepta CM-1 A membrane (manufactured by Tokuyama Co., Ltd.), and Aciplex K101 membrane (manufactured by Asahi Kasei Corporation) are used.

  In the electrode chamber 6, the electrode chamber 8, the auxiliary salt chamber 15, the auxiliary material chamber 16, the product chamber 17, and the raw material chamber 18, chamber liquid according to the purpose is prepared to a predetermined concentration and a predetermined amount, respectively. Operate in circulation.

  In the electrode chambers 6 and 8, for example, an aqueous sodium hydrogen sulfate solution having a concentration of 2% by mass to 10% by mass is prepared.

  In the product chamber 17, for example, a dilute solution of a concentrate to be recovered, such as a 1% by mass aqueous hydroiodic acid solution, is prepared.

  The raw material chamber 18, for example, is supplied with a raw material liquid which is an aqueous solution containing fluorine such as industrial waste liquid and useful anions.

  It is preferable that the raw material liquid has a fluorine concentration of 1 g / L or less.

  Moreover, it is preferable that the raw material liquid has an anion concentration of 1% or more to be recovered.

  To this raw material liquid is added a cation (polyvalent cation) that forms a cation complex with a fluoride ion, and the pH is maintained so as not to cause precipitation of the positive ion added to the raw material liquid. Drive 1

Cations, for example, aluminum ions, polyaluminium ions, zirconium oxide ions, zirconium ions, calcium ions, magnesium ions, iron ions, scandium ions, gallium ions, Gadori two-ion, indium ion, of vanadium ions and lanthanum ions It is preferred to add at least one cation.

  Further, it is preferable to add 0.3 or more moles of cations per metal in total with respect to fluorine contained in the raw material solution.

  When a cation such as aluminum ion is added at a molar ratio of 1 times or more to fluoride ion, fluorine forms a complex having a positive charge with aluminum ion. When it has a positive charge, it can pass through the second cation exchange membrane 14 but can not pass through the second anion exchange membrane 13 so that the movement of fluorine to the product chamber 17 is suppressed.

  Further, when the electrodialysis operation is advanced, aluminum ions in the raw material chamber 18 move into the auxiliary salt chamber 15. Since the aluminum ion is stronger in charge than the aluminum-fluorine complex, it is presumed that the transfer rate to the auxiliary salt chamber 15 is high.

  Therefore, in order to keep the aluminum / fluorine molar ratio above a certain level until the end of electrodialysis, it is preferable to add an excessive amount of aluminum ions to the stock solution before starting the electrodialysis.

  Thus, the movement of fluorine to the product room (concentrate) is suppressed until the end of the electrodialysis.

  In order to obtain a useful anion concentrate (product liquid) containing no fluoride ion from the raw material liquid containing fluoride ion and a useful anion, the fluoride ion and the cation may be added to the raw material liquid. It is effective to add the above-mentioned cation (multivalent cation) such as aluminum ion to form a complex and maintain the pH of the raw material solution so that precipitation of the added cation does not occur. It is preferable to separate by double displacement electrodialysis in which cations in the solution do not move to the concentrate side.

  Specifically, the raw material solution is an aqueous solution containing fluoride ions of 1 g / L or less, and the iodine concentration is 50 g / L or more and 200 g / L or less, the pH is 2 or less, and the aluminum ion concentration is 2000 mg / L or less It is preferable to prepare using hydrochloric acid or water so that

  An aqueous solution of a strong acid such as sulfuric acid or hydrochloric acid is supplied to the auxiliary material chamber 16. Specifically, for example, sulfuric acid with a concentration of 5% by mass to 20% by mass or hydrochloric acid with a concentration of 5% by mass to 20% by mass is supplied.

  A diluted solution of an aqueous solution of an acid or a salt by-produced corresponding to the liquid in the auxiliary material chamber 16 is supplied to the auxiliary salt chamber 15, 22, 23. Specifically, for example, an aqueous sodium hydrogen sulfate solution having a concentration of 2% by mass to 5% by mass is supplied.

  In addition, when the liquid property of the raw material chamber 18 and the auxiliary salt chamber 15 becomes near neutral, precipitation of aluminum hydroxide is generated. If aluminum hydroxide precipitates, aluminum ions from the solution will be reduced, which may not only reduce the aluminum / fluorine ratio but also lead to flow path blockage in the electrodialysis tank 1. Therefore, the source chamber 18 and the auxiliary salt chamber 15 are controlled to maintain the acidity or sufficiently added with a mineral acid or the like having a slower moving speed than useful anions before starting the dialysis operation. It is preferred to maintain the acidity.

  During operation of the electrodialysis tank 1, the temperature in each room is maintained at or below the heat resistance temperature of the ion exchange membrane to be used.

  Then, when a voltage is applied between the electrodes 2 and 3, the anions contained in the respective chamber solutions are attracted to the anode side, and the cations are attracted to the cathode side.

  Anions can move through the anion exchange membranes 11, 13 but can not pass through the cation exchange membranes 5, 7, 12, 14, 21.

  Therefore, the iodide ion in the raw material chamber 18 passes through the second anion exchange membrane 13 to the positive electrode side to move to the product chamber 17, and further passes through the first cation exchange membrane 12 from the product chamber 17. Then, since it can not move to the auxiliary material chamber 16, it is separated and concentrated as a product liquid in the product chamber 17. Similarly, hydrogen ions in the auxiliary material chamber 16 pass through the first cation exchange membrane 12 and move to the product chamber 17. The cations in the feed chamber 18 pass through the second cation exchange membrane 14 and are separated and concentrated in the auxiliary salt chamber 15.

As a result, the iodide ion (I ⁻ ) in the raw material liquid supplied into the raw material chamber 18 by electrodialysis in the electrodialysis tank 1 and the hydrogen ion (H ⁺ ) of the liquid in the auxiliary raw material chamber 16 The hydroiodic acid is produced by the double displacement dialysis reaction, and the concentration of the hydroiodic acid in the concentrate in the product chamber 17 increases, and the acid or salt in the liquid in the auxiliary material chamber 16 The concentration of sodium hydrogen sulfate, for example, increases.

  Further, the concentration of hydroiodic acid in the raw material liquid in the raw material chamber 18 of the raw material system and the concentration of the acid in the liquid in the auxiliary raw material chamber 16 gradually decrease, and the current The value decreases.

  After the current value is sufficiently reduced, the electrodialysis in the electrodialysis tank 1 is once stopped, and an appropriate amount of the room fluid in the material chamber 18 and the auxiliary material chamber 16 of the material system is extracted as a processing solution. The auxiliary raw material chamber 16 is again filled with the liquid that becomes the raw material.

  Then, the concentrate in the product room 17 of the production system and the room fluid in the auxiliary salt compartments 15, 22 and 23 are left partially for use as a raw material for the next electrodialysis, and the remaining is extracted as a production liquid. In addition, you may operate continuously by supplying and withdrawing each chamber liquid continuously.

  By repeating the above-described steps, it is possible to obtain an aqueous solution containing a useful anion at a high concentration, such as, for example, hydroiodic acid or the like, using a fluorine-containing raw material liquid.

  Here, if the raw material solution is made acidic, most of the fluorine will be uncharged hydrogen fluoride molecules, and there should be no electrical transfer and it should stay in the raw material chamber 18, but the raw material containing fluorine was used so far According to the result of the electrodialysis, even if the raw material chamber 18 is made acidic, several to several tens percent of the fluorine in the raw material chamber 18 may move to the product chamber 17 through the second anion exchange membrane 13 confirmed. In addition, movement to the auxiliary salt chamber 22 via the second cation exchange membrane 14 was also confirmed.

  From this, in the case of hydrogen fluoride having a small molecular size, the second anion exchange membrane 13 is not electrically carried out with the simple diffusion and the movement of water caused by the difference in osmotic pressure between the raw material chamber 18 and the product chamber 17. It is considered to move through the second cation exchange membrane 14.

  Therefore, in order to obtain the product liquid which does not contain fluorine, it is inadequate only by keeping a raw material liquid acidic.

  Therefore, by adding a substance that is easily bonded to fluorine and setting the fluoride to be a fluoride having a molecular size larger than that of hydrogen fluoride, non-electrical transfer of fluorine is suppressed. Further, a polyvalent cation which is easily bonded to fluorine is added to form a complex having a positive charge of fluorine and a polyvalent cation, whereby the product is introduced to the product chamber 17 through the second anion exchange membrane 13. Significantly suppress the movement of fluorine.

  That is, the fluorine fixed as a cation complex moves to the auxiliary salt chamber 15 via the second cation exchange membrane 14, but moves to the product chamber 17 via the second anion exchange membrane 13. Is prevented. In the case of a double displacement electrodialysis method having a structure in which the cations in the raw material chamber 18 do not move to the product chamber 17, the moving direction of fluorine is only on the side of the secondary salt chamber 15 via the second cation exchange membrane 14. Thus, a useful anion concentrate free of fluorine can be obtained in only one electrodialysis step.

  The concentration of fluorine in the concentrate after electrodialysis is preferably 2 mg / L or less, and more preferably 1 mg / L or less of the concentration of fluorine in the concentrate before and after electrodialysis.

  The fluorine remaining in the stock solution and the subsalt solution after useful anion recovery can be easily removed by known methods such as pH adjustment or coprecipitation with cations added by the addition of lime milk.

  Here, reference 1 (Fujii Tona et al., “Quantitation of fluoride ion in salt by solid phase extraction with zirconium supported ion chromatography by ion chromatography”, Journal of the Japan Seawater Society, Saltwater Research Center Foundation, In 2013, Vol. 67, No. 1, P. 41-46), in order to determine fluorine in a solution containing fluorine and iodine, under acidity with hydrochloric acid, a zirconium oxide-supporting weak cation exchange resin was added to the solution. A method is disclosed in which only fluorine is separated by adsorbing the fluorine and desorbing with alkalinity to analyze by ion chromatography. That is, it is believed that the zirconium oxide ion forms a complex with fluorine under strong acidity and the complex breaks down under basicity. In addition, even if the zirconium oxide ion forms a complex with fluorine, the complex is considered to be in the form of cation since it is still fixed to the weak cation exchange resin.

  The document states that the presence of aluminum ions significantly interferes with the adsorption of fluorine on the zirconium oxide-supported weak cation exchange resin. That is, aluminum ions are considered to form a complex more stable than zirconium oxide ions under strong acidity.

  For the complex formed by the combination of fluoride ion and aluminum ion, see Reference 2 (Taura Katsuhiko et al., “Regarding the absorption of fluorine and aluminum to the living body and the interaction in the living body,” 1996-1999. Grant-in-Aid for Scientific Research on Science (Basic research (b) (2)) Report on research results, Tohoku University Dental Hospital, March 1999. The complex is an aluminum monofluoride divalent cation, an aluminum difluoride monovalent cation, an aluminum trifluoride aluminum tetrafluoride anion, an aluminum pentafluoride divalent depending on the concentration and ratio of fluorine and aluminum ions. Anion and any one of six types of aluminum hexafluoride trivalent anion are present. That is, it is thought that the complex which consists of an aluminum ion and a fluorine can be made only to the complex of a cation type by adjusting the molar ratio of aluminum / fluorine under acidity to more than fixed.

  Then, if the fluorine is fixed only to the cation type complex, the fluorine can not electrically move into the product liquid through the second anion exchange membrane 13. In addition, the passage of the second anion exchange membrane 13 due to diffusion is also significantly restricted by the fact that the molecular size is larger than that of the hydrogen fluoride molecules and by having a positive charge.

Therefore, the polyvalent cations added to the raw material solution, for example, aluminum ions, polyaluminium ions, zirconium oxide ions, zirconium ions, calcium ions, magnesium ions, iron ions, scandium ions, gallium ions, Gadori two-ion, indium Those which form stable complexes with ions such as fluorine ions such as vanadium ions and lanthanum ions, and which do not react with water in water to form an oxide solid are preferable.

  When polyvalent cations with high toxicity, strict effluent standards, or radioactive substances are used, it is necessary to completely recover the added ions after dialysis, and the post-process becomes complicated. It is not preferable because the cost is as low as possible.

  In addition, the above-mentioned polyvalent cations can be used alone or in combination.

  With respect to the anions to be added to the cation to be added, insoluble or hardly soluble salts are formed with the components in the raw material solution and the components in the auxiliary salt solution, and the components in the raw material solution and the components in the auxiliary salt solution If it does not react, it can be selected as appropriate, but the ion selectivity between the useful anion to be recovered by the second anion exchange membrane 13 separating the raw material chamber 18 and the product chamber 17 and the ions to be added What has is desirable. Specifically, when the useful anion to be recovered is a monovalent anion and the second anion exchange membrane 13 is a monovalent selective anion exchange membrane, the anion to be paired is, for example, a sulfate ion. And polyvalent anions such as phosphate ions are preferred. In addition, when the useful anion to be recovered is iodide ion, it is also possible to use chloride ion whose anion selectivity is sufficiently lower than that of iodide ion.

  And according to the above-mentioned one embodiment, since the cation which forms a cation complex with fluorine is added to a materials liquid, and in order to maintain the pH which precipitation of the added cations does not produce, By forming a complex with the ions, the movement of fluorine from the raw material solution to the concentrate can be restricted. Therefore, a useful anion concentrate that does not contain fluorine can be obtained from the raw material liquid that contains fluorine by the electrodialysis method.

  In the method for separating useful anions according to the present invention, for example, if recovery of useful anions such as iodide ion is performed, it is possible to separate useful anions from fluoride ion by one electrodialysis alone. Become. Further, even in the conventional electrodialysis method, cations such as aluminum ions can be added to the raw material solution and applied only to maintain a predetermined pH, and there is no need to provide a new process or facility, so existing facilities are installed. It is easy to apply to

  For example, in the case of using aluminum ion as a cation, a generally-available aluminum sulfate solution may be used, and the process is simple without powder input and the like, which is very advantageous also in cost.

  Furthermore, the fluorine remaining in the raw material liquid and the auxiliary salt solution after useful anion recovery can be precipitated and separated by a known method, and it is useful to be generated by adhering to the fluorine-containing precipitate. It is also possible to prevent the loss of ions.

  In addition, since it is not necessary to consider the loss of useful anions due to adhesion, it is sufficient for the precipitate to be in the form of a slurry having a high water content, and the operation such as strict filtration or washing is not necessary. The operation such as transportation after treatment is very easy.

  Furthermore, since this precipitation separation step can be performed by so-called outer step separate from the useful anion collection step, the process can be simplified and easily processed.

  As in the embodiment described above, concentration separation by double displacement electrodialysis using one set of electrodialysis tank 1 with four chambers and four membranes separates anions and cations in raw material chamber 18. However, the present invention is not limited to such a configuration, and any electrodialysis method using an electrodialysis tank having a configuration in which cations in the raw material chamber do not move to the product chamber can be appropriately applied. For example, a three-chamber electrodialysis method without an auxiliary salt chamber, an electrodialysis method without an auxiliary material chamber using a bipolar membrane, or the like may be used, and the number of chambers and the number of membranes are four or more. May be

  Useful anions to be separated are not limited to iodide ions, but various anions which can be used for any purpose, such as chloride ions, bromide ions and organic acid ions.

  Hereinafter, specific examples and comparative examples of the present invention will be described.

Example 1
Electrodialysis was performed using the electrodialysis tank 1 shown in FIG. 1 (G4 type electrodialysis tank manufactured by Asahi Kasei Corp., one set of 4 membranes, 5 sets, effective area 0.02 m ² / sheet). went.

  For the cation exchange membranes 5, 7, 12, 14, 21 a ceremion CMV manufactured by Asahi Glass Co., Ltd. was used. As the second anion exchange membrane 13, Seremion ASV manufactured by Asahi Glass Co., Ltd., which is a monovalent anion selective membrane, was used. As the first anion exchange membrane 11, Seremion AMV manufactured by Asahi Glass Co., Ltd., which is an anion selective permeation membrane, was used.

  Each chamber liquid comprises 1700 mL of raw material chamber liquid (composition: iodide ion 80 g / L, fluoride ion 55.6 mg / L, aluminum ion 500 mg / L, pH 1), product compartment liquid 720 mL (composition: iodide ion 10 g / L ), Auxiliary material chamber liquid 1600 mL (composition: sulfuric acid 50 g / L), sub salt chamber liquid 1000 mL (composition: sodium hydrogen sulfate 17 g / L), electrode liquid 1500 mL (composition: sodium hydrogen sulfate 50 g / L), It was supplied to each room.

  Then, after completion of the operation at 8.5 V for 2 hours, the liquid amounts and fluorine concentrations of the raw material chamber 18, the product chamber 17 and the auxiliary salt chamber 22 were measured.

  The determination of the fluorine concentration was analyzed by ion chromatography after removing iodine using a silver-supported cation exchange resin cartridge.

  The measurement results before and after the dialysis operation are shown in Table 1.

  As shown in Table 1, there was almost no change in the fluorine concentration and the amount of fluorine before and after dialysis in the product chamber 17, and the fluorine in the raw material chamber 18 hardly moved to the product chamber 17.

Example 2
The same electrodialysis tank 1 and ion exchange membranes 5, 7, 11, 12, 13, 14 and 21 as in Example 1 were used.

Each chamber liquid is a raw material chamber liquid 1700 mL (Composition: 80 g / L of iodide ion, 55.6 mg / L of fluoride ion, 5.8 g / L of zirconium oxychloride (ZrOCl ₂ · 8H ₂ O), pH 1) Product room liquid 720 mL (composition: iodide ion 10 g / L), auxiliary material room liquid 1600 mL (composition: sulfuric acid 50 g / L), sub salt room liquid 1000 mL (composition: sodium hydrogen sulfate 17 g / L), electrode liquid 1500 mL (composition Composition: Sodium hydrogen sulfate (50 g / L) was prepared and supplied to each chamber.

  In the same manner as in Example 1, after the operation at 8.5 V for 2 hours was finished, the liquid amounts, fluorine concentration and the like of the raw material chamber 18, the product chamber 17 and the auxiliary salt chamber 22 were measured.

  The measurement results before and after the dialysis operation are shown in Table 2.

  As shown in Table 2, there was almost no change in the fluorine concentration and the amount of fluorine before and after dialysis in the product chamber 17, and the fluorine in the raw material chamber 18 did not move to the product chamber 17.

  Further, there was almost no change in the fluorine concentration and the amount of fluorine before and after dialysis in the auxiliary salt chamber 22, and the fluorine in the raw material chamber 18 hardly moved to the auxiliary salt chamber 22.

[Comparative example]
The same electrodialysis apparatus and ion exchange membrane as in Example 1 were used.

  Each chamber liquid is 1700 mL of material chamber liquid (composition: iodide ion 80 g / L, fluoride ion 55.6 mg / L, pH 1), product chamber liquid 720 mL (composition: iodide ion 10 g / L), auxiliary material chamber liquid The solution was adjusted to 1600 mL (composition: 50 g / L of sulfuric acid), 1000 mL of sub-salt liquid (composition: 17 g / L of sodium hydrogen sulfate), and 1500 mL of an electrolyte (composition: 50 g / L of sodium hydrogen sulfate) and supplied to each chamber.

  In the same manner as in Example 1, after the operation at 8.5 V for 2 hours was finished, the liquid amounts, fluorine concentration and the like of the raw material chamber 18, the product chamber 17 and the auxiliary salt chamber 22 were measured. The measurement results before and after the dialysis operation are shown in Table 3.

  The fluorine concentration and the amount of fluorine in the product chamber 17 are significantly increased after dialysis compared to before dialysis, and about one half of the fluorine in the raw material chamber 18 has moved to the product chamber 17.

  INDUSTRIAL APPLICABILITY The present invention can be used, for example, as a technology for separating and recovering useful anions from fluorine-containing industrial waste liquid and chemical product intermediates, natural salt salt-derived saline, etc. so as not to contain fluorine. In addition, it can be used as a method of removing in advance anions that interfere when removing fluorine in the chelate adsorption method or the like.

1 Electrodialysis tank
11 first anion exchange membrane
12 first cation exchange membrane
13 second anion exchange membrane
14 second cation exchange membrane
15 auxiliary salt chamber
16 auxiliary material room
17 product rooms
18 material room

Claims (8)

An anion separation method for separating and concentrating anions into a product liquid from a raw material liquid containing fluorine together with anions other than fluorine by electrodialysis,
As the electrodialysis method, a first anion exchange membrane, a first cation exchange membrane, a second anion exchange membrane, and a second cation exchange membrane are sequentially disposed, and these ion exchange membranes sequentially An electrodialysis method using an electrodialysis tank divided into a salt room, an auxiliary material room, a product room, and a raw material room, and arranged repeatedly as a four room four membranes from the auxiliary salt room to the second cation exchange membrane as one set Three-chamber electrodialysis method without sub-salt chamber or electrodialysis method without sub-material chamber using bipolar membrane,
In the raw material solution, add a cation that forms a complex with fluorine,
A method of separating an anion, comprising maintaining the raw material liquid at a pH at which precipitation of the added cation does not occur. The method of separating anions according to claim 1 , wherein the cation which forms a complex with fluorine is a polyvalent cation . The cation which forms a complex with fluorine is aluminum ion, polyaluminum ion, zirconium oxide ion, zirconium ion, calcium ion, magnesium ion, iron ion, scandium ion, gallium ion, gadolinium ion, indium ion, vanadium ion and lanthanum ion The method for separating anions according to claim 1 or 2 , which is at least one of the following . The fluorine concentration of the raw material solution is less than 1000 mg / L,
The fluorine concentration in a product liquid is 2 mg / L or less. The separation method of the anion according to any one of claims 1 to 3. The method for separating anions according to any one of claims 1 to 4, wherein the amount of increase in fluorine concentration in the product liquid before and after electrodialysis is 1 mg / L or less. The anion concentration other than fluorine of the raw material liquid is 1% or more. The method for separating anions according to any one of claims 1 to 5. The method for separating an anion according to any one of claims 1 to 6, wherein the anion is at least one of an iodide ion, a bromide ion, a chloride ion and an organic acid ion. The method for separating anions according to any one of claims 1 to 7, wherein the cation is added in a total amount of 0.3 times by mole or more per metal in total with respect to the fluorine contained in the raw material solution.

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